Application of Exergoeconomics to the Analysis and Optimization of Process Systems

ＡｐｐｌｉｃａｔｉｏｎｏｆＥｘｅｒｇｏｅｃｏｎｏｍｉｃｓｔｏｔｈｅＡｎａｌｙｓｉｓａｎｄＯｐｔｉｍｉｚａｔｉｏｎｏｆＰｒｏｃｅｓｓＳｙｓｔｅｍｓＡｐｐｌｉｃａｔｉｏｎｏｆＥｘｅｒｇｏｅｃｏｎｏｍｉｃｓｔｏｔｈｅＡｎａｌｙｓｉｓａｎｄＯｐｔｉｍｉｚａｔ...     

Experimental and Numerical Investigation of Enhancement of Heat and Mass Transfer in Adsorbent Beds

ＥｘｐｅｒｉｍｅｎｔａｌａｎｄＮｕｍｅｒｉｃａｌＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＥｎｈａｎｃｅｍｅｎｔｏｆＨｅａｔａｎｄＭａｓｓＴｒａｎｓｆｅｒｉｎＡｄｓｏｒｂｅｎｔＢｅｄｓＬｉｕＺｈｅｎｙａｎ；ＦｕＺｈｕｍａｎ；ＧｅＸｉｎｓｈｉ；ＳｕＹｕｅｈｏｎｇ；...     

An Experimental and Numerical Study of Natural Convection Heat Transfer in Horizontal Annuli between Eccentric Cylinders

ＡｎＥｘｐｅｒｉｍｅｎｔａｌａｎｄＮｕｍｅｒｉｃａｌＳｔｕｄｙｏｆＮａｔｕｒａｌＣｏｎｖｅｃｔｉｏｎＨｅａｔＴｒａｎｓｆｅｒｉｎＨｏｒｉｚｏｎｔａｌＡｎｎｕｌｉｂｅｔｗｅｅｎＥｃｃｅｎｔｒｉｃＣｙｌｉｎｄｅｒｓ￥ＷａｎｇＳｕｏｆａｎｇ（Ｄｅｐａｒｔｍ...     

A New Calculation Method of the Axial and Radial Velocity and Grade──Efficiency for High──Efficiency Cyclones

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JOURNAL OF THERMAL SCIENCE（JTS） International Journal of Thermal and Fluid Sciences

ＪＯＵＲＮＡＬＯＦＴＨＥＲＭＡＬＳＣＩＥＮＣＥ（ＪＴＳ）ＩｎｔｅｒｎａｔｉｏｎａｌＪｏｕｒｎａｌｏｆＴｈｅｒｍａｌａｎｄＦｌｕｉｄＳｃｉｅｎｃｅｓ￥ＥｄｉｔｏｒｉａｌＡｄｖｉｓｏｒｙＢｏａｒｄＪＯＵＲＮＡＬＯＦＴＨＥＲＭＡＬＳＣＩＥＮＣＥ（ＪＴＳ）Ｉ...     

Simulating Experimental Investigation on the Safety of Nuclear Heating Reactor in Loss—of —Coolant Accidents

ＳｉｍｕｌａｔｉｎｇＥｘｐｅｒｉｍｅｎｔａｌＩｎｖｅｓｔｉｇａｔｉｏｎｏｎｔｈｅＳａｆｅｔｙｏｆＮｕｃｌｅａｒＨｅａｔｉｎｇＲｅａｃｔｏｒｉｎＬｏｓｓ－ｏｆ－ＣｏｏｌａｎｔＡｃｃｉｄｅｎｔｓＳｉｍｕｌａｔｉｎｇＥｘｐｅｒｉｍｅｎｔａｌＩｎｖｅｓｔｉｇ...     

Analysis of Solidiflcation in the Presence of High Rayleigh Number Convection in an Enclosure

ＡｎａｌｙｓｉｓｏｆＳｏｌｉｄｉｆｌｃａｔｉｏｎｉｎｔｈｅＰｒｅｓｅｎｃｅｏｆ　ＨｉｇｈＲａｙｌｅｉｇｈＮｕｍｂｅｒＣｏｎｖｅｃｔｉｏｎｉｎａｎＥｎｃｌｏｓｕｒｅＹｕｗｅｎＺｈａｎｇ（ＳｃｈｏｏｌｏｆＥｎｅｒｇｙａｎｄＰｏｗｅｒＭａｃｈｉｎｅｒｙＥｎ...     

A Technique for Producing Drinking Water from Air Using Adsorbents Driven by Solar Energy：Theoretical and Experimental Research

ＡＴｅｃｈｎｉｑｕｅｆｏｒＰｒｏｄｕｃｉｎｇＤｒｉｎｋｉｎｇＷａｔｅｒｆｒｏｍＡｉｒＵｓｉｎｇＡｄｓｏｒｂｅｎｔｓＤｒｉｖｅｎｂｙＳｏｌａｒＥｎｅｒｇｙ：ＴｈｅｏｒｅｔｉｃａｌａｎｄＥｘｐｅｒｉｍｅｎｔａｌＲｅｓｅａｒｃｈ￥ＣｈｏｕＱｉａｏｌｉ；Ｓｕ...     

Non－Darcian and Anisotropic Anisotropic Effects on Natural Convection in Horizontal Porous Media Enclosure

Ｎｏｎ－ＤａｒｃｉａｎａｎｄＡｎｉｓｏｔｒｏｐｉｃＡｎｉｓｏｔｒｏｐｉｃＥｆｆｅｃｔｓｏｎＮａｔｕｒａｌＣｏｎｖｅｃｔｉｏｎｉｎＨｏｒｉｚｏｎｔａｌＰｏｒｏｕｓＭｅｄｉａＥｎｃｌｏｓｕｒｅＺｈａｎｇＪｉｎｇｚｈｏｕ（ＤｅｐａｒｔｍｅｎｔｏｆＰｏｗｅｒ...     

JOURNAL OF THERMAL SCIENCE(JTS) International Journal of Thermal and Fluid Sciences

ＪＯＵＲＮＡＬＯＦＴＨＥｘｔＭＡＬＳＣＩＥＮＣＥ（ＪＴＳ）ＩｎｔｅｒｎａｔｉｏｎａｌＪｏｕｒｎａｌｏｆ　ＴｈｅｒｍａｌａｎｄＦｌｕｉｄＳｃｉｅｎｃｅｓＪＯＵＲＮＡＬＯＦＴＨＥｘｔＭＡＬＳＣＩＥＮＣＥ（ＪＴＳ）ＩｎｔｅｒｎａｔｉｏｎａｌＪｏｕｒｎａｌｏ...     

Finite size thermoeconomic optimization for irreversible heat engines

An optimization analysis for an irreversible heat engine has been carried out based on a new thermoeconomic optimization criterion. The thermoeconomical objective function has been taken as the power output per unit total cost. In the analysis, the irreversibility effects due to heat transfer across finite temperature differences, the heat leak loss between the external heat reservoirs and internal dissipation of the working fluid are taken into account. The maximum of the objective function and the corresponding optimal conditions has been derived analytically. The effects of technical and economical parameters on the global and optimal performances have been investigated.     

Effects of combined heat transfer on the thermo-economic performance of irreversible solar-driven heat engines

A thermo-economic performance analysis and optimization has been carried out for an irrversible solar-driven heat engine with losses due to heat transfer across finite temperature differences, heat leak and internal irreversibilities. In the considered heat engine model, heat transfer from the hot reservoir is assumed to be simultaneous radiation and convection mode and the heat transfer to the cold reservoir is assumed to be convection mode. The effects of the technical and economical parameters on the thermo-economic performance have been investigated in order to see the collective effects of the radiation and convection modes of heat transfer. Also the optimal performance parameters of the heat engine, such as the thermal efficiency, temperatures of the working fluid and the ratio of heat transfer areas have been discussed in detail.     

Optimal Performance Characteristics of Subcritical Simple Irreversible Organic Rankine Cycle

Based on the theory of finite time thermodynamics, a subcritical simple irreversible organic Rankine cycle (SSIORC) model considering heat transfer loss and internal irreversible losses is established in this paper. The total heat transfer surface area is taken as a constraint, and R245fa is adopted as working fluid of the cycle in the performance optimization. The evaporator heat transfer surface area and mass flow rate of the working fluid are optimized to obtain the maximum power output and thermal efficiency of the SSIORC, respectively. In addition, the influences of the internal irreversibilities on the optimal performances are also investigated. The results show that when the evaporator heat transfer surface area is varied, the relationship between power output and thermal efficiency is a loop-shaped curve, and there exist maximum power output and thermal efficiency points, respectively. However, the two maximum points are very close to each other. When the mass flow rate of the working fluid is varied, the relationship between power output and thermal efficiency is a parabolic-like curve. With the decreases of expander and pump irreversible losses, the performances of the irreversible SSORC are close to those of the endoreversible SSORC with the only loss of heat transfer loss.     

不可逆半导体固态热离子制冷器性能分析和优化

建立了考虑外部有限速率传热过程和热源间热漏的不可逆半导体固态热离子制冷器模型,基于非平衡热力学和有限时间热力学理论导出了热离子制冷器的制冷率和制冷系数的表达式;对比分析了不可逆热离子制冷器与可逆热离子制冷器的发射电流密度特性、电极温度特性以及制冷系数特性;研究了不可逆系统的制冷率与制冷系数最优性能,得到了制冷率和制冷系数的最优运行区间;通过数值计算,详细讨论了外部传热以及内部导热、热源间热漏损失、热源温度、外加电压、半导体材料势垒等设计参数对热离子装置性能的影响。在总传热面积一定的条件下,进一步优化了高、低温侧换热器的面积分配以获得最佳的制冷率和制冷系数特性。结果表明,由于存在内部和外部的不可逆性,热离子装置的发射电流密度及制冷系数都会明显降低;不可逆半导体固态热离子制冷器的制冷率与制冷系数特性呈扭叶型;合理地选外加电压、势垒等参数,可以使制冷器设计于最大制冷率或最大制冷系数的状态。     

Numerical evaluation and the effects of geometrical and operational parameters on thermal performance of the shell and double coil tube heat exchanger

Heat exchangers are extensively used in various industries. In this study, the impact of geometric and flow parameters on the performance of a shell and double helical coil heat exchanger is studied numerically. The investigated geometric parameters include external coil pitch, internal coil pitch, internal coil diameter, and coil diameter. The influences of considered geometrical parameters are analyzed on the output temperature of the hot and cold fluid, convective heat transfer coefficient, pressure drop, and average Nusselt number. Water is considered as working fluid in both shell and tube. As an innovation, double helical coils are used instead of one in the heat exchanger. To compare the obtained results accurately, in each section, the heat transfer area (coil outer surface) is kept constant in all models. The results show that the geometrical parameters of double helical coils significantly affect the heat transfer rate.     

Entropy generation and its relation to heating and cooling requirements of a metal hydride hydrogen storage reactor

In this paper a metal hydride hydrogen storage reactor is analyzed from heat and mass transfer and entropy generation points of view. A transient two dimensional energy equation along with suitable reaction kinetics and entropy balance equation is solved numerically. Results are obtained keeping hydrogen flow rates constant during absorption and desorption. For a fixed mass of metal hydride in the reactor the amount of hydrogen transferred and the time in which the transfer takes place are kept fixed. Using the mathematical model the entropy generated during the process and the external cooling and heating fluid requirements are obtained. Results show how improvement in the design and/or operating conditions leads to reduced cooling and heating requirements and lower entropy generation. For the system considered in the study the internal heat transfer characteristics of the hydride bed are seen to influence the reactor performance significantly. With improved bed heat transfer the required heat transfer fluid temperature during desorption can be reduced and that during absorption can be increased significantly. This automatically leads to lower entropy generation and a more economic system operation. It is expected that the methodology proposed and the results presented in this study will be useful in the optimal design of metal hydride reactors for a variety of practical applications, including hydrogen storage.     

Passive heat and moisture removal from a natural vented enclosure with a massive wall

Simultaneous transport of heat and moisture by conjugate natural convection in a partial enclosure with a solid wall is investigated numerically. Moist air motions are driven by the external temperature and concentration differences imposed across enclosures with different ambient moisture conditions. The Prandtl number and Schmidt number used are 0.7 and 0.6, respectively. The fluid, heat and moisture transports through the cavity and solid wall are, respectively, analyzed using the streamlines, heatlines and masslines, and the heat and mass transfer potentials are also explained by the variations of overall Nusselt and Sherwood numbers. The numerical simulations presented here span a wide range of the main parameters (heat and mass diffusion coefficient ratios, solid wall thickness and thermal Rayleigh numbers) in the domain of aiding and opposing buoyancy-driven flows. It is shown that the heat transfer potential, mass transfer potential, and volume flow rate can be promoted or inhibited, depending strongly on the wall materials and size, thermal and moisture Rayleigh numbers.     

Heat and mass transfer within a vertical pipe with a surface heating element of variable size

Heat and mass transfer due to upstream fluid flow in a vertical pipe which is heated in some region due to an external heating element on the surface of the pipe is considered. Unlike most studied in the literature which consider heating uniformly over the entire pipe, we allow for the heater to act over a smaller sub-region of the pipe surface. We first derive a heat and mass transfer model to describe the velocity, pressure, and temperature evolution in a vertical pipe under the assumption of cylindrical symmetry. Using a finite element method we are able to obtain numerical simulations to this model. We compare solutions under a variety of different heater configurations, in order to understand how the size and placement of the heating element on the surface of the pipe will modify the thermal properties of the fluid. We find that a smaller heating element placed near the top of the pipe can still deliver sufficient heat so that the temperature of fluid exiting the top of the pipe has desirable thermal properties for a specific application, and in such cases it is not necessary to heat the entire length of the pipe. Such a configuration could be more efficient, as it requires less material for the heating element, while also requiring less energy for the heating. On the other hand, if the heating element is too small, or poorly placed along the pipe, then it may not be possible to obtain desirable thermal properties in the fluid that would have been possible with a heating element covering the entire pipe length.     

Thermodynamic optimisation of the integrated design of a small‐scale solar thermal Brayton cycle

The Brayton cycle's heat source does not need to be from combustion but can be extracted from solar energy. When a black cavity receiver is mounted at the focus of a parabolic dish concentrator, the reflected light is absorbed and converted into a heat source. The second law of thermodynamics and entropy generation minimisation are applied to optimise the geometries of the recuperator and receiver. The irreversibilities in the recuperative solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In a small‐scale open and direct solar thermal Brayton cycle with a micro‐turbine operating at its highest compressor efficiency, the geometries of a cavity receiver and counterflow‐plated recuperator can be optimised in such a way that the system produces maximum net power output. A modified cavity receiver is used in the analysis, and parabolic dish concentrator diameters of 6 to 18 m are considered. Two cavity construction methods are compared. Results show that the maximum thermal efficiency of the system is a function of the solar concentrator diameter and choice of micro‐turbine. The optimum receiver tube diameter is relatively large when compared with the receiver size. The optimum recuperator channel aspect ratio for the highest maximum net power output of a micro‐turbine is a linear function of the system mass flow rate for a constant recuperator height. For a system operating at a relatively small mass flow rate, with a specific concentrator size, the optimum recuperator length is small. For the systems with the highest maximum net power output, the irreversibilities are spread throughout the system in such a way that the internal irreversibility rate is almost three times the external irreversibility rate. Copyright © 2011 John Wiley & Sons, Ltd.     

Integration of a free-piston Stirling engine and a moving grate incinerator

The feasibility of recovering the waste heat from a small-scale incinerator (designed by Industrial Technology Research Institute) and generating electric power by a linear free-piston Stirling engine is investigated in this study. A heat-transfer model is used to simulate the integration system of the Stirling engine and the incinerator. In this model, the external irreversibility is modeled by the finite temperature difference and by the actual heat transfer area, while the internal irreversibility is considered by an internal heat leakage. At a fixed source temperature and a fixed sink temperature, the optimal engine performance can be obtained by the method of Lagrange multipliers.From the energy and mass balances for the interesting incinerator with the feeding rate at 16 t/d, there is enough otherwise wasted energy for powering the Stirling engine and generate more than 50 kW of electricity.